首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   218篇
  免费   15篇
耳鼻咽喉   12篇
儿科学   4篇
基础医学   22篇
口腔科学   52篇
临床医学   14篇
内科学   48篇
神经病学   8篇
特种医学   4篇
外科学   30篇
预防医学   12篇
眼科学   10篇
药学   5篇
肿瘤学   12篇
  2022年   2篇
  2021年   8篇
  2020年   4篇
  2019年   3篇
  2018年   7篇
  2017年   4篇
  2016年   4篇
  2015年   1篇
  2014年   5篇
  2013年   6篇
  2012年   16篇
  2011年   15篇
  2010年   10篇
  2009年   5篇
  2008年   13篇
  2007年   14篇
  2006年   13篇
  2005年   7篇
  2004年   6篇
  2003年   14篇
  2002年   14篇
  2001年   9篇
  2000年   11篇
  1999年   6篇
  1998年   1篇
  1997年   2篇
  1996年   2篇
  1995年   1篇
  1994年   1篇
  1993年   2篇
  1992年   4篇
  1991年   5篇
  1990年   2篇
  1989年   3篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
  1984年   2篇
  1983年   1篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1974年   1篇
  1972年   1篇
排序方式: 共有233条查询结果,搜索用时 15 毫秒
1.
2.
3.
Live attenuated HIV vaccines offer a means to introduce exogenous sequences into the viral genome to target the virus elimination in vivo. Foreign genes inserted into the nef region of HIV-1 NL4-3 were found to be rapidly deleted following virus infection and/or replication, in a size dependent manner, in the human fetal Thymus/Liver implants of severe combined immunodeficient mouse (SCID-hu) model. When the murine heat stable antigen (HSA) of 283 bp was substituted into HIV-1 nef region, the viral loads in vivo were comparable to the negative control nef attenuated HIV-1, and the reporter HSA gene was not deleted upon infection. However, the murine Thy1.2 gene (505 bp) substituted into the nef attenuated HIV-1, upon infection and replication, deleted 441 bp in vitro and 437 bp in vivo, of the inserted Thy1.2 gene. When the enhanced green fluorescence protein (eGFP) gene (720 bp) was substituted for nef, virus replication was aborted in vivo in the Thy/Liv implants, as seen by the background levels of viral loads, comparable to mock infected implants, and the eGFP gene was deleted. When the herpes simplex virus thymidine kinase gene, HSV-TK (1.15 kbp), or HSA gene, was substituted into the viral vpr gene, TK but not HSA gene was deleted, upon infection in vitro. Moreover, NL-TKI reporter virus with both intact nef and vpr genes shows deletion of TK gene both in vitro and in vivo. Excision of foreign genes occurred within the exogenous segments but not in the viral own regions. These results suggest that larger "suicide" genes introduced via HIV-1 can be deleted upon infection. However, smaller size nucleotide sequences or genes (approximately 300 bp) inserted in place of viral nef or vpr gene may be used to target the virus or its components, for attack and elimination in vivo, and thus have implications for the development of live attenuated HIV vaccines.  相似文献   
4.
Summary Modifying effects of age, sex, and mouse strain on diethylnitrosamine (DEN) carcinogenesis have been investigated in C57BL/6Jx C3HeB/FeJ F1 (B6C3F1) and C3HeB/FeJxA/J F1 (C3AF1) hybrid mice. Animals each received four IP injections of 1.5 or 3.0 g DEN/g body weight. The first injections were administered on days 1, 15, or 42 of life. Subsequent treatments were delivered at 3-, 6-, and 6-day intervals, respectively. Mice were kept under observation for the remaining life-span. DEN treatment induced tumors in liver, lungs, and forestomach in descending order of frequency. The majority of the induced liver tumors were hepatocellular carcinomas. Animals treated as newborns and infants developed significantly more liver tumors than animals that were treated as young adults. Newborn and infant females developed liver tumors at a later age (B6C3F1) and with a lower incidence (C3AF1) than similarly treated males. The B6C3F1 mice developed more hepatocellular carcinomas and a higher rate of pulmonary metastases than the C3AF1 mice. In contrast, C3AF1 mice developed lung tumors with a higher incidence and multiplicity than B6C3F1 hybrids. Forestomach tumors were observed also with a slightly but significantly higher incidence in C3AF1 mice.Dedicated to Professor Hermann Druckrey on the occasion of his 80th birthdayThese investigations have been supported in part by Contracts NIH-NCI-69-2087 and NO1-CO-43317 from the National Cancer Institute  相似文献   
5.
We evaluated the antialbuminuric advantage of cilnidipine, an N/L-type calcium channel blocker (CCB), compared with L-type CCBs in diabetic patients with normoalbuminuria and microalbuminuria. The study was a multicenter, non-randomized crossover trial. Participants were 90 type 2 diabetic patients exhibiting either normo- or microalbuminuria, and undergoing CCB treatment for ≥6 months prior to study entry. The CCB at the time of entry was continued for the first 6 months (Period 1). Treatment was subsequently switched from cilnidipine to an L-type CCB, or vice versa, for the second 6-month observation period (Period 2). During Period 1, the L-type CCB group showed a significant increase of urinary albumin excretion (UAE) over time, while the cilnidipine group showed no significant elevation. During Period 2, switching of the treatment from the L-type CCB to cilnidipine resulted in significant reduction of the UAE, whereas switching from cilnidipine to the L-type CCB resulted in no significant change in the UAE. This study demonstrated that the antialbuminuric effect of Cilnidipine, but not the L-type CCBs, was sustained even in patients treated for a long time. In addition, the antialbuminuric effect can be anticipated after switching from an L-type CCB to cilnidipine, but not vice versa.  相似文献   
6.
7.
8.
In order to study the effects of residual stenosis on myocardial salvage, we created 99% coronary stenosis with or without contrast washout delay at reperfusion in six groups of dogs. In Group A (n = 8), the artery was occluded for 1h before being fully reperfused. In Group B (n = 9), the artery was occluded for 1h, then subjected to 6h of 99% stenosis without contrast washout delay. In Group C (n = 8), the artery was occluded for 1h, followed by 1 week of 99% stenosis without contrast washout delay. In Group D (n = 10), again the artery was occluded for 1h, then subjected to 6h of 99% stenosis with contrast washout delay. In Group E (n = 8), the artery was occluded for 7h, then fully reperfused for 1 week. Finally, in Group F (n = 8), the occlusion lasted for a full week. All dogs were sacrificed 1 week after occlusion. In Group A, myocardial creatine phosphokinase activity (CK) in the inner layer was 43.8 +/- 12.5% that of non-infarcted myocardium. Myocardial CK in Group B (46.5 +/- 7.4%) was little different but in Group C it dropped to 26.6 +/- 8.4%, suggesting that 99% residual stenosis is not deleterious if it is continued for 6h or less but that it will result in considerable depletion of myocardial CK, it is is sustained for 1 week. In Group D, myocardial CK dropped markedly to 11.3 +/- 3.7%, little different from that for either Group E (13.3 +/- 2.6%) or Group F (9.3 +/- 3.3%).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
9.
10.
OBJECTIVE/HYPOTHESIS: A wide variety of substances have been shown to promote neuritic extension after nerve injury. An obstacle to achieving the maximal benefit from these substances has been the difficulty in effectively delivering the substances over a protracted time course that promotes maximal, directed growth. In this study the delivery of a growth-promoting substance through a biodegradable conduit, using materials originally designed for drug delivery applications, was hypothesized to promote more robust neural regeneration than through conduits lacking the substance. The objectives of this study were to create a growth factor-loaded biodegradable nerve guidance conduit, and to assess in vivo nerve regeneration through the conduit compared with that through conduits lacking the substance. MATERIALS/METHODS: Inosine, a purine analogue thought to promote axonal extension following neural injury, was loaded into cylindrical polymer foams composed of a polylactide-co-glycolide copolymer. First, in vitro extravasation of inosine was measured over a several week period using spectrophotometry. Second, the foams were fashioned into single-channel cylindrical nerve guidance conduits via a novel, low-pressure injection molding technique. The conduits were then used to bridge 7-mm defects in the rat sciatic nerve (n = 8). Control conduits lacking inosine were implanted into another set of animals as controls (n = 12). RESULTS: In vitro spectrophotometric measurements indicated appreciable leaching of inosine from the loaded foams over a period of at least 9 weeks. In the in vivo model, after 10 weeks, a higher percentage cross sectional area composed of neural tissue existed through the inosine-loaded conduits compared with controls (mean 44%, SD 7.5% vs. 36%, SD 8.6%, respectively). A difference was also found in mean fiber diameter between the two groups, with the inosine-loaded tubes showing a statistically significantly larger diameter than controls (P < .05). CONCLUSIONS: A nerve regeneration conduit was successfully created that delivers growth promoting substances over a protracted time course. In an in vivo model, the presence of inosine, a purine analogue, yielded neural regeneration whose histological features suggest possible superior long-term motor function.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号